Question

question 7 (1 point)
what is the primary function of the electron transport chain?
to directly generate atp by substrate - level phosphorylation.
to produce carbon dioxide.
to pump protons across the inner mitochondrial membrane to create an electrochemical gradient.
to break down glucose into 2 molecules of pyruvate.

Explanation:

1. Analyze the first option: Substrate - level phosphorylation generates ATP in glycolysis and the citric acid cycle, not the electron transport chain (ETC). So this option is incorrect.
2. Analyze the second option: Carbon dioxide is produced in the citric acid cycle (from decarboxylation reactions), not by the ETC. So this option is incorrect.
3. Analyze the third option: The ETC consists of protein complexes in the inner mitochondrial membrane. As electrons pass through these complexes, protons (\(H^+\)) are pumped from the mitochondrial matrix to the intermembrane space, creating an electrochemical gradient (proton - motive force). This gradient is then used by ATP synthase to generate ATP. So this option correctly describes the primary function of the ETC.
4. Analyze the fourth option: The breakdown of glucose into 2 molecules of pyruvate is the process of glycolysis, not related to the ETC. So this option is incorrect.

Answer:

C. To pump protons across the inner mitochondrial membrane to create an electrochemical gradient.